The invention relates to a server system and a control method for the same. The present invention is preferably applicable for a file sharing server providing a virtual server environment, for example.
Conventionally, such a system that one file sharing server provides a plurality of virtual file sharing servers (hereinafter referred to as virtual server, virtual NAS (Network Attached Storage)) to integrate a large number of file sharing servers is widely known.
Integration of a plurality of file sharing servers to one file sharing server is effective for simplifying management of file sharing servers, establishment of power saving by suppressing power consumed by the file sharing server. There is an OS (Operating System) division method as a system which provides that virtual server,
A virtual server is realized by an OS division method in which function provided by physical device such as a disc and a network adapter and an OS such as process space and Name Space is divided for each virtual server. The OS division method alleviates the load on OS resource management process by standardizing memory management and process management module among virtual servers.
On the other hand, there is N-way cluster technology where a plurality of file sharing servers for providing virtual servers are used and causing the virtual servers are moved (hereinafter to be referred to as virtual server migration or failover) among those file sharing servers. According to that technology, maintainability such as countermeasure for file sharing server fault and replace of file sharing servers can be realized.
Moreover, the N-way cluster technology realizes an appropriate load balancing for the entire cluster by moving the virtual servers among the file sharing servers based on I/O (Input/Output) load information of the virtual servers. Here, Japanese Patent Application Laid-open No. 2004-227127 is known as patent describing a method of realizing a virtual OS related to the virtual server. In addition, Japanese Patent Application Laid-open No. 2007-233783 is known as a method of obtaining I/O load information by a storage to carry out load balancing.
In the N-way cluster technology, I/O load information is obtained for every virtual server in order to realize appropriate load balancing. In addition, in the N-way cluster technology, the virtual server is temporarily halts. The halt virtual server is started up by another file sharing server. Such an arrangement enables a virtual server to move to another file sharing server to establish load balancing.
In the N-way cluster technology, currently, a method of obtaining access information for every disc is adopted as a method of obtaining a load. That is, for the N-way cluster technology, access information (I/O information) on a disc allocated to a certain virtual server is obtained; the operation state of the virtual server is estimated; and, thereby, movement of the virtual server is controlled.
Here, in the case of estimating the operation state of a virtual server based on access information of the disc, the total I/O amount will be an amount of adding all disc access of the virtual servers. For example, in the case where disc access taking place in file copying and the process such as file data search are carried out simultaneously, the I/O amount of those two processes is summed and, thereby, the operation state of the virtual servers is estimated in the N-way cluster technology. Therefore, the N-way cluster technology cannot determine whether the disc access is important data process.
Accordingly, current the operation state estimation on the virtual servers based on total I/O amount on disc access gives rise to such a problem that unnecessary movement of virtual servers takes place.
In the case of the preceding example, the process such as file copy that is not so important causes occurrence of virtual server movement. For movement of the virtual servers, service is temporarily suspended and, therefore, delay in important process such as file data search occasionally takes place.
In addition, according to the type of file access protocol, connection is occasionally disconnected to halt an operation of a client apparatus connected to the file sharing server. Since the movement of a virtual server accompanies a halt and startup of the virtual server, the load to the file sharing server is heavy. Accordingly, the unnecessary movement of the virtual server has to be avoided as much as possible.